Light-reflective anisotropic conductive paste and light-emitting device

Abstract

A light-reflective anisotropic conductive paste is used as an anisotropic conductive paste when a light-emitting device is produced by flip-chip mounting a light-emitting element such as a light-emitting diode element (LED) on a wiring board. The light-reflective anisotropic conductive paste includes light-reflective insulating particles, in order to improve light emission efficiency without providing, in the LED, a light-reflecting layer that causes an increase in manufacturing cost. With the light-reflective anisotropic conductive paste, a reduction in bonding strength of the light-emitting element to the wiring board in a high-temperature environment can be suppressed, and a reduction in conduction reliability after a TCT can also be suppressed. In the light-reflective anisotropic conductive paste, conductive particles and the light-reflective insulating particles are dispersed in a thermosetting resin composition. The thermosetting resin composition contains an epoxy compound and a thermal catalyst-type curing agent.

The invention claimed is: 
     
       1. A light-reflective anisotropic conductive paste used to connect a light-emitting element to a wiring board by anisotropic conductive connection, the light-reflective anisotropic conductive paste comprising a thermosetting resin composition, conductive particles, and light-reflective insulating particles, the conductive particles and the light-reflective insulating particles being dispersed in the thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy compound and a thermal cationic polymerization catalyst-type curing agent in the form of an aromatic sulfonium compound represented by the formula (1): 
       
         
           
           
               
               
           
         
         where in the formula (1), R 1  is an aralkyl group, R 2  is a loweralkyl group, and R 3  is a hydrogen atom or a loweralkoxycarbonyl group, X represents a halogen atom, and n is an integer from 1 to 3. 
       
     
     
       2. The light-reflective anisotropic conductive paste according to  claim 1 , wherein the aromatic sulfonium compound is a sulfonium borate complex represented by any of the following formulas (1a), (1b), (1c), and (1A): 
       
         
           
           
               
               
           
         
       
     
     
       3. The light-reflective anisotropic conductive paste according to  claim 1 , wherein an amount of the thermal cationic polymerization catalyst-type curing agent added in the thermosetting resin composition is 0.5 to 3 parts by mass based on 100 parts by mass of the epoxy compound. 
     
     
       4. The light-reflective anisotropic conductive paste according to  claim 1 , wherein each of the light-reflective insulating particles is an inorganic particle selected from the group consisting of titanium oxide, boron nitride, zinc oxide, and aluminum oxide. 
     
     
       5. The light-reflective anisotropic conductive paste according to  claim 4 , wherein a refractive index (JIS K7142) of the light-reflective insulating particles is larger than a refractive index (JIS K7142) of a cured product of the thermosetting resin composition. 
     
     
       6. The light-reflective anisotropic conductive paste according to  claim 1 , wherein an amount of the light-reflective insulating particles added is 40 to 120 parts by mass based on 100 parts by mass of the thermosetting resin composition. 
     
     
       7. A light-emitting device comprising a light-emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 1 , the light-emitting element being flip-chip mounted on the wiring board through the light-reflective anisotropic conductive paste. 
     
     
       8. The light-emitting device according to  claim 7 , wherein the light-emitting element is a light-emitting diode element. 
     
     
       9. A light-emitting device comprising a light-emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 1 , the light-transmitting element being flip-chip mounted on the wiring board through the light-reflective anisotropic conductive paste. 
     
     
       10. The light-emitting device according to  claim 9 , wherein the light-emitting element is a light-emitting diode element. 
     
     
       11. A light-reflective anisotropic conductive paste used to connect a light-emitting element to a wiring board by anisotropic conductive connection, the light-reflective anisotropic conductive paste comprising a thermosetting resin composition, conductive particles, and light-reflective insulating particles, the conductive particles and the light-reflective insulating particles being dispersed in the thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy compound and a thermal catalyst-type curing agent, wherein the light-reflective insulating particles are resin-coated metal particles obtained by coating surfaces of scale-like or spherical silver particles with an insulating resin. 
     
     
       12. A light-emitting device comprising a light-emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 11 , the light-transmitting element being flip-chip mounted on the wiring board through the light-reflective anisotropic conductive paste. 
     
     
       13. A light-reflective anisotropic conductive paste used to connect a light-emitting element to a wiring board by anisotropic conductive connection, the light-reflective anisotropic conductive paste comprising a thermosetting resin composition, conductive particles, and light-reflective insulating particles, the conductive particles and the light-reflective insulating particles being dispersed in the thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy compound and a thermal catalyst-type curing agent, wherein each of the conductive particles is a light-reflective conductive particle including a core particle coated with a metal material and a light reflecting layer disposed on a surface of the core particle and formed of at least one type of inorganic particle selected from titanium oxide particles, zinc oxide particles, and aluminum oxide particles. 
     
     
       14. The light-reflective anisotropic conductive paste according to  claim 13 , wherein an amount added of the light-reflective conductive particles is 1 to 100 parts by mass based on 100 parts by mass of the thermosetting resin composition. 
     
     
       15. A light emitting device comprising a light emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 13 , the light-transmitting element being flip-chip mounted on the wiring board anisotropic conductive paste. 
     
     
       16. A light-reflective anisotropic conductive paste used to connect a light-emitting element to a wiring board by anisotropic conductive connection, the light-reflective anisotropic conductive paste comprising a thermosetting resin composition, conductive particles, and light-reflective insulating particles, the conductive particles and the light-reflective insulating particles being dispersed in the thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy compound and a thermal catalyst-type curing agent, and each of the light-reflective insulating particles is titanium oxide. 
     
     
       17. The light-reflective anisotropic conductive paste according to  claim 16 , wherein the epoxy compound is an alicyclic epoxy compound. 
     
     
       18. The light-reflective anisotropic conductive paste according to  claim 16 , wherein an amount of the thermal catalyst-type curing agent added in the thermosetting resin composition is 0.5 to 3 parts by mass based on 100 parts by mass of the epoxy compound. 
     
     
       19. The light-reflective anisotropic conductive paste according to  claim 16 , wherein a refractive index (JIS K7142) of the light-reflective insulating particles is larger than a refractive index (JIS K7142) of a cured product of the thermosetting resin composition. 
     
     
       20. The light-reflective anisotropic conductive paste according to  claim 16 , wherein an amount of the light-reflective insulating particles added is 40 to 120 parts by mass based on 100 parts by mass of the thermosetting resin composition. 
     
     
       21. A light-emitting device comprising a light emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 16 , the light-transmitting element being flip-chip mounted on the wiring board through the light-reflective anisotropic conductive paste. 
     
     
       22. An anisotropic conductive paste used to connect a light-emitting element to a wiring board by anisotropic conductive connection, the anisotropic conductive paste comprising a thermosetting resin composition, conductive particles, and light-reflective insulating particles being dispersed in the thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy compound and a thermal catalyst-type curing agent, and the anisotropic conductive paste has a light reflectivity of 30% or higher to a wavelength of 40 nm. 
     
     
       23. A light-emitting device comprising a light-emitting element, a wiring board, and the light-reflective anisotropic conductive paste according to  claim 22 , the light-transmitting element being flip-chip mounted on the wiring board through the light-reflective anisotropic conductive paste.